Dyes which are known as dyestuffs or pigments, are broadly employed in various uses, such as dying material for fiber, coloring material for resin or paints, photograph, printing, copying machines, image forming material in a printer and light-absorbing material of a filter. Recently, there have been proposed a variety of image forming dyes used for hard color copy employing ink-jet recording, electrophotography, silver salt photography, thermal transfer recording and the like. Along with development of electronic imaging, demands for filter dyes for use in solid camera tubes or color liquid crystal televisions and dyes for use in photo-recording mediums employing semiconductor lasers have increased and the usable field of dyes has been expanded.
In color copiers or color laser printers employing an electrophotography system are used toners composed of coloring material dispersed in resin or toners composed of coloring material adhered onto the resin particle surface. Allowing coloring material to adhere onto the resin particle surface colors only the surface and renders it difficult to achieve sufficient coloring effects. Further, problems arise with the release of the coloring material from the surface such that charging behavior varies or the surface of a fixing roller is stained. Accordingly, there are broadly used toners in which coloring material is dispersed in the interior of the toner particle. Performance required in such toners includes color reproducibility, image transparency in over-head project (or OHP) and light fastness. JP-A No. 62-157051, 62-255956 and 6-118715 (hereinafter, the term, JP-A refers to Japanese patent Application Publication) disclosed toners in which pigments as coloring material were dispersed within the toner particle. While these toners are superior in light fastness, they are insoluble and easily coagulated, producing problems such as lowered transparency or varied hue. JP-A Nos. 3-276161, 2-207273 and 2-207274 disclosed toners using dyes as coloring material. While these toners exhibit high transparency and cause no variation in hue, there is problem in lightfastness.
Color filters require high transparency so that a so-called dying method using dyes for coloring has been conducted. For instance, a dyeable photosensitive material is coated on the substrate such as glass and subjected to pattern exposure corresponding to one filter color, then, unexposed areas are washed off in the development stage and the remaining pattern portion is dyed with a dye. The foregoing-operation is successively repeated for all filter colors to prepare a color filter. In this method, the use of dyes enhances transparency, leading to superior optical properties as a color filter. However, lightfastness and heat resistance are limited therein so that coloring material exhibiting various superior resistance properties and enhanced transparency has been desired. Organic pigments exhibiting superior lightfastness and heat resistance have been employed in place of dyes. However, color filters using pigments proved to be difficult to obtain optical properties achieved by dyes.
In dyes usable in the respective uses described above, the following properties are commonly desired to be provided. Thus, it is to exhibit preferred hue in color reproduction, to exhibit appropriate spectral absorption characteristics, to be superior in image fastness, such as lightfastness, moisture-resistance and chemical resistance, and to exhibit enhanced molar absorptivity.